In a large mixing bowl, combine the pork belly, pork loin, liver, port, garlic, juniper berries, peppercorns, dried mixed herbs and a little salt. Mix well with your hands, breaking the mixture up as much as possible. Cover and leave to marinate for 1 hour.
After 1 hour, preheat the oven to 150°C.
Spoon the meat mixture into a 2lb terrine bowl, spreading it out evenly with the back of a spoon. Half-fill a roasting tray with boiling water then sit the terrine bowl in the water. Bake in the oven for 90-120 minutes until the internal temperature of the pâté reaches 65°C. Use a meat thermometer to test the internal temperature. Remove once is reaches 65°C, then leave it to cool to one side.
As it is cooling, you can prepare the aspic jelly. Place all the ingredients for the jelly in a heavy-based saucepan and set over a moderate heat. Whisk until the gelatine softens, then continue to whisk as you bring the mixture to the boil. Simmer for a few minutes, then pour the liquid very carefully through the crusty layer that has formed on top through a muslin lined sieve into a clean bowl. Cover and leave the mixture to cool to one side.
Once cool, pour on top of the cooled pate and chill the dish for a few hours until the jelly has set. Remove 5-10 minutes before serving.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.